Double-stage triggering type time-controllable full-degradable material

Abstract

The invention discloses a two-stage trigger type time-controllable full-degradable material and a preparation method thereof, and belongs to the field of bio-based degradable high polymer materials. Aiming at the defects that a traditional degradable material is uncontrollable in time sequence, easy to attenuate in performance, poor in environmental adaptability and unrecyclable in resource, the invention provides the degradable material which is composed of a basic polymer, a modification auxiliary agent, a functional auxiliary agent and a microorganism synergistic component, and the degradable material is formed through gradient feeding, pre-plasticizing, copolymerization and step-by-step granulation processes. Two-stage degradation triggering, chitosan embedded microorganism catalysis and gradient structure collaborative design are adopted, and a closed-loop recycling and regenerating process is matched. According to the invention, the material is stable and reliable in use stage, is efficiently degraded after expiration, improves the adaptability to complex environment, optimizes mechanical and processing properties, realizes cyclic utilization of biomass resources, solves the industrial problem that degradation and use properties are difficult to consider, and has excellent practicability and environmental protection value.

Description

Technical Field

[0001] This invention belongs to the field of bio-based biodegradable polymer materials technology, specifically relating to a two-stage triggered time-controllable fully degradable material. Background Technology

[0002] As global efforts to combat plastic pollution continue, fully biodegradable materials, represented by polylactic acid (PLA) and modified starch, have become a core technological route to replace petroleum-based non-degradable plastics. Currently, most fully biodegradable materials used on a large scale in the industry are prepared using conventional methods involving the physical blending of starch and PLA with the addition of a single degradation aid. However, this approach faces several long-standing technical bottlenecks in practical applications and industrial promotion.

[0003] First, the degradation process is indiscriminate natural hydrolysis, making it impossible to effectively separate the service stage from the degradation stage. Within the preset service life, the material is prone to premature hydrolysis, oxidative chain scission, and mechanical property degradation, leading to packaging damage, film cracking, and structural failure. This makes it impossible to guarantee the structural stability and functional reliability of the product during its service life, and thus difficult to meet the application requirements of high-precision timing control.

[0004] Second, the degradation rate control method is singular, relying solely on the blending of simple additives such as organic acids and inorganic fillers to achieve rate adjustment. The degradation cycle is greatly affected by environmental temperature, humidity, and soil microbial content, with the cycle fluctuation range usually exceeding sixty days. It cannot achieve precise quantitative control, and the same formula shows significant differences in performance under different regions and climatic conditions, lacking the basis for stable industrial application.

[0005] Third, the material system is a homogeneous blend structure with the same components in the surface and inner layers. This can easily lead to problems such as premature degradation of the surface layer while the inner layer remains intact, or a delayed overall degradation initiation. It is impossible to balance mechanical retention rate and degradation initiation efficiency, which is a recognized technical contradiction in this field.

[0006] Fourth, conventional biodegradable materials are too dependent on environmental conditions. In low-temperature environments below 10 degrees Celsius, in arid or sandy soil environments, the hydrolysis rate and microbial activity are greatly reduced, the degradation cycle is greatly extended, and they may even fail to degrade for a long time, resulting in extremely poor environmental adaptability.

[0007] Fifth, starch and polylactic acid have a large difference in polarity and poor interfacial compatibility. After simple blending, the material is brittle, has low tensile strength, and poor processing fluidity, making it unsuitable for various molding processes such as blown film, injection molding, and extruded sheet, thus limiting its application scenarios. Summary of the Invention

[0008] To address the numerous shortcomings of existing technologies, this invention discloses a dual-stage triggered time-controllable fully degradable material and its preparation method, achieving adjustable degradation cycle, high mechanical property retention during the service life, rapid and complete degradation after the service life ends, and stable degradation efficiency even under low temperature and drought conditions, while also taking into account excellent mechanical strength, processing fluidity and raw material recycling rate.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0010] A two-stage triggered time-controlled fully degradable material, comprising a base polymer component, a modified additive component, a functional additive component, and a microbial synergistic component;

[0011] The basic polymer component is a copolymer of preplasticized modified starch and polylactic acid, with lubricants and processing aids added during the preplasticization process;

[0012] The modified additive components include polyethylene glycol compatibilizers, maleic anhydride grafting agents, and plasticizers;

[0013] The functional additive components include an inorganic reinforcing agent, a two-stage degrading agent, a toughening agent, and a composite solvent. The two-stage degrading agent includes a stable-phase slow-release antioxidant and an accelerated-phase pH / enzyme-responsive degrading agent.

[0014] The microbial synergistic component includes a chitosan-embedded Bacillus / Pseudomonas complex bacterial agent;

[0015] Each component is prepared through a process of gradient feeding, preplasticization, copolymerization, stepwise addition of functional additives, and granulation.

[0016] Furthermore, in the dual-stage degradation agent, the stable-phase slow-release antioxidant is a microencapsulated hindered phenolic product, with an addition amount of 0.2%-0.4% of the mass of the basic polymer component; the accelerated-phase pH-responsive degradation agent is polyaspartic acid or polyglutamic acid, with an addition amount of 1%-2% of the mass of the basic polymer component.

[0017] Furthermore, in the microbial synergistic component, the chitosan microspheres have a particle size of 5-20 μm, the bacterial agent encapsulation rate is not less than 85%, and the addition amount is 0.5%-1.2% of the mass of the basic polymer component.

[0018] Furthermore, a gradient feeding process is adopted: the surface layer accounts for 15%-25% of the total material mass, and fast degradation aids and microbial agents are added to the surface layer; the inner layer accounts for 75%-85% of the total material mass, and slow degradation aids and inorganic reinforcing agents are added to the inner layer.

[0019] Furthermore, the material in a natural soil environment:

[0020] The stabilization period is from day 0 to day T, where T is the preset degradation cycle, and the mechanical properties retention rate during this stage is not less than 80%.

[0021] The accelerated degradation period is from day T to day T+60, during which the degradation rate is no less than 90%.

[0022] Where T is 180 days to 720 days, and the degradation time error is no more than ±10 days.

[0023] Furthermore, the PEG compatibilizer has a molecular weight of 2000-6000 and is added at 3%-8% of the mass of the basic polymer component; the maleic anhydride grafting agent has a grafting rate of 0.5%-2% and is added at 1%-3% of the mass of the basic polymer component.

[0024] Furthermore, the inorganic reinforcing agent is calcium carbonate or talc powder with a particle size of 1000-3000 mesh, and the addition amount is 5%-15% of the mass of the basic polymer component; the toughening agent is epoxidized soybean oil, polylactic acid elastomer or ethylene-vinyl acetate copolymer, and the addition amount is 5%-20% of the mass of the basic polymer component.

[0025] A method for preparing a two-stage triggered time-controllable fully degradable material includes the following steps:

[0026] Pre-plasticization modification: Starch, polylactic acid, lubricant and processing aid are mixed and plasticized and granulated by twin-screw extruder at 140℃-170℃ to obtain pre-plasticized granules;

[0027] Gradient feeding: A layered feeding process is adopted, with fast degradation aids, microbial agents and primary solvents added to the surface layer, and slow degradation aids, inorganic enhancers and primary antioxidants added to the inner layer;

[0028] Copolymerization reaction: Copolymerize at 160℃-180℃ for 20-40 min to obtain copolymer;

[0029] Secondary plasticizing: Add plasticizer and slow-release antioxidant, and plasticize at 150℃-170℃ for 10-20 minutes;

[0030] Toughening modification: Add toughening agent, compatibilizer, auxiliary agent and secondary solvent, mix at 145℃-165℃ for 10-15min;

[0031] Granulation: Extrusion granulation yields fully degradable resin particles;

[0032] Closed-loop recycling: Degradation products are collected and polylactic acid is reprocessed through fermentation-polymerization, thus realizing raw material recycling.

[0033] Furthermore, the microbial agent is encapsulated with chitosan microspheres at an encapsulation temperature of 40℃-60℃ for 2-4 hours; in the closed-loop recovery step, the fermentation temperature of the degradation product is 35℃-45℃ for 72-96 hours, and the purity of the obtained L-lactic acid is not less than 95%.

[0034] Furthermore, the degradation cycle of the material is extended by no more than 20 days under low temperature or drought conditions of 10°C, the mechanical property retention rate is not less than 75%, and the degradation products can be recycled in a closed loop through fermentation-polymerization process to prepare polylactic acid, with a raw material recycling rate of not less than 75%.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention, through a holistic technical concept encompassing two-stage triggered degradation, gradient structure construction, encapsulated microbial synergistic catalysis, and closed-loop recycling throughout the entire lifecycle, achieves synergistic effects across multiple dimensions, including component design, structural construction, preparation process, and recycling. This effectively overcomes common industry challenges faced by traditional degradable materials, such as uncontrollable degradation timing, easy performance degradation within the service life, difficulty in balancing mechanical and degradation properties, poor environmental adaptability, and inability to recycle resources. The resulting material exhibits excellent structural stability and mechanical reliability during its service life, achieving orderly and efficient complete degradation after the preset service life. It also significantly enhances adaptability to complex natural environments, broadening the material's application scenarios and geographical scope. Through multi-component interface modification and gradient distribution design, the material's processability and comprehensive mechanical properties are optimized, enabling it to adapt to various conventional plastic processing technologies and providing a solid foundation for industrial mass production. The closed-loop regeneration process enables the resource-based recycling of degradation products, improving the material's environmental friendliness and economic efficiency throughout its entire lifecycle. The synergistic effects of these technical features achieve comprehensive performance unattainable by traditional single-technology methods. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention proposes a two-stage triggered, time-controllable fully degradable material and its preparation method, as detailed below:

[0039] (I) Two-stage trigger-type time-controllable fully degradable material product solution

[0040] The dual-stage triggered time-controllable fully degradable material of this invention consists of four parts: a basic polymer component, a modified auxiliary component, a functional auxiliary component, and a microbial synergistic component. Each component is integrated into a single process through gradient feeding, preplasticization, copolymerization, stepwise addition of functional auxiliary components, and granulation. Under low temperature (10°C) or drought conditions, the degradation cycle of the material is extended by no more than 20 days, the mechanical property retention rate is no less than 75%, and the degradation products can be recycled through a closed-loop fermentation-polymerization process to prepare polylactic acid, with a raw material recycling rate of no less than 75%.

[0041] 1. Basic polymer components

[0042] The basic polymer component is a copolymer of preplasticized modified starch and polylactic acid, which serves as the continuous phase matrix of the material and undertakes the functions of structural support and mechanical load-bearing.

[0043] The starch is selected from corn starch, tapioca starch or potato starch. Before being compounded with polylactic acid, it undergoes pre-plasticization modification treatment. During the pre-plasticization process, lubricants and processing aids are added. The crystalline structure of the starch is destroyed by thermomechanical shearing, reducing the intermolecular hydrogen bonding forces, improving the melt flowability and thermal stability of the starch, and at the same time improving the interfacial wettability between starch and polylactic acid, reducing phase separation and interfacial defects.

[0044] Lubricants are used to reduce the frictional resistance between materials and equipment during processing, while further improving the starch plasticizing effect; processing aids are used to improve the thermal stability and shear fluidity of the system, and avoid thermal oxidative aging and local scorching during the pre-plasticization process.

[0045] Polylactic acid is L-polylactic acid, with a molecular weight range suitable for extrusion granulation and molding processing. It forms a semi-interpenetrating network copolymer structure with pre-plasticized starch, ensuring the continuity and uniformity of the matrix.

[0046] 2. Modified additive components

[0047] The modified additives include polyethylene glycol compatibilizers, maleic anhydride grafting agents, and plasticizers. These three types of additives work synergistically to improve the interfacial compatibility, molecular chain activity, and processing fluidity of the blend system.

[0048] Among them, polyethylene glycol compatibilizers have a molecular weight of 2000~6000 and are added at 3%~8% of the mass of the base polymer component. As an amphiphilic polymer, one end of its molecular chain forms hydrogen bonds with the hydroxyl groups of starch, and the other end forms entanglement with the polylactic acid molecular chain, which greatly reduces the interfacial tension between the two phases, eliminates interfacial pores and stress concentration, and improves the tensile strength and elongation at break of the material.

[0049] Maleic anhydride grafting agents have a grafting rate of 0.5% to 2% and are added at 1% to 3% of the mass of the base polymer component. Under thermal shear conditions, they undergo a grafting reaction with polylactic acid molecular chains, increasing the polarity and reactivity of the polylactic acid molecular chains, further strengthening the binding strength with modified starch, and forming a chemically bonded interface structure rather than a physically blended interface.

[0050] Plasticizers are used to reduce the melt processing temperature and melt viscosity of blended systems, widen the processing window, avoid thermal damage to subsequently added microbial agents and heat-sensitive additives caused by high-temperature processing, and ensure the activity and effectiveness of functional components.

[0051] 3. Functional additive components

[0052] The functional additives include inorganic reinforcing agents, two-stage degradation agents, toughening agents, and composite solvents, which are the core components for achieving two-stage triggered degradation and enhanced mechanical properties.

[0053] The inorganic reinforcing agent is calcium carbonate or talc powder with a particle size of 1000 mesh to 3000 mesh. The amount added is 5% to 15% of the mass of the basic polymer component. Micron-sized inorganic powder is used and is uniformly dispersed in the matrix to play the roles of physical reinforcement, dimensional stability and regulation of degradation rate, while improving the heat deformation resistance and processing dimensional stability of the material.

[0054] The dual-stage degradation agent consists of a stable-phase slow-release antioxidant and an accelerated-phase pH-responsive or enzyme-responsive degradation agent, forming the core of the dual-stage time-series control. The stable-phase slow-release antioxidant is a microencapsulated hindered phenolic product, added at 0.2%–0.4% of the base polymer component mass. Utilizing a microencapsulation structure, it slowly releases during the material's service life, continuously capturing heat, oxygen, and free radicals, inhibiting polymer chain oxidation and scission, ensuring no significant degradation of mechanical properties within the preset period, and maintaining reliability. The accelerated-phase pH-responsive degradation agent is polyaspartic acid or polyglutamic acid, added at 1%–2% of the base polymer component mass. After the material's preset service life ends, triggered by changes in environmental pH or hydrolytic enzyme signals secreted by microorganisms, it rapidly dissociates and catalyzes the breakage of polylactic acid ester bonds and amylose glycoside bonds, causing a rapid decrease in polymer molecular weight, disintegration of the material's macrostructure, and entry into the rapid degradation stage. This achieves an active triggering switch from stable service to efficient degradation.

[0055] The toughening agent is epoxidized soybean oil, polylactic acid elastomer, or ethylene-vinyl acetate copolymer. The addition amount is 5% to 20% of the mass of the base polymer component. It is used to improve the impact resistance and elongation at break of the material, overcome the defects of starch polylactic acid system that is brittle and easy to crack, and adapt to the molding and use requirements of various forms such as films, sheets, and structural parts.

[0056] The composite solvent adopts a graded solvent system, which is divided into primary solvent and secondary solvent, and is added at different processing stages to improve the uniformity of additive dispersion, promote interfacial compatibility and reaction grafting, and avoid performance fluctuations caused by additive agglomeration.

[0057] 4. Microbial synergistic components

[0058] The microbial synergistic component contains a chitosan-embedded Bacillus and Pseudomonas complex microbial agent, which is the core functional component for environmental adaptive degradation. Its addition amount is 0.5% to 1.2% of the mass of the basic polymer component.

[0059] Bacillus and Pseudomonas were selected as highly efficient degrading strains that can secrete esterases, amylases, and glycoside hydrolases to directionally catalyze the biodegradation of polylactic acid and starch. Chitosan, a natural biodegradable polymer, serves as the encapsulation carrier. Chitosan microspheres, with a particle size of 5-20 μm and an encapsulation rate of no less than 85%, form a microsphere coating structure during processing, isolating the bacteria from damage caused by high-temperature melts and shear forces, ensuring the bacteria remain viable after granulation. Once the material enters the natural environment, the chitosan microspheres absorb water and swell, slowly releasing the composite bacterial agent. The bacteria colonize and multiply in the environment, continuously secreting degrading enzymes, forming a synergistic catalysis with the chemically responsive degrading agent, significantly improving the degradation rate and reducing dependence on environmental temperature and humidity.

[0060] Chitosan microspheres have suitable particle size and encapsulation rate, ensuring uniform dispersion in the matrix without agglomeration and without compromising the mechanical continuity of the material.

[0061] 5. Gradient structure and molding process characteristics

[0062] The material is prepared using a gradient feeding process, forming a differentiated structure between a surface layer and an inner layer. The surface layer accounts for 15%–25% of the total material mass, while the inner layer accounts for 75%–85%. The surface layer is loaded with fast-degrading auxiliaries and microbial agents, which preferentially respond to environmental signals, initiating surface degradation and providing a pathway for microbial colonization. The inner layer is loaded with slow-degrading auxiliaries and inorganic reinforcing agents, which bear the main mechanical load-bearing role during the service life, ensuring structural integrity.

[0063] The overall preparation process adopts a multi-stage process of preplasticization, copolymerization, stepwise addition of additives, gradient feeding and final granulation to achieve orderly dispersion, interfacial bonding and functional gradient distribution of each component. This is different from the traditional one-step blending process and ensures the stable realization of dual-stage functions from the preparation principle.

[0064] Meanwhile, the material exhibits a clear two-stage degradation characteristic in natural soil environments. The stable period is from day 0 to day T, where T is the preset degradation cycle, and the mechanical properties retention rate during this stage is no less than 80%. The accelerated period is from day T to day T+60, and the degradation rate during this stage is no less than 90%. The value of T ranges from 180 days to 720 days, and the degradation time error does not exceed ±10 days. The degradation cycle can be customized and controlled according to the needs of different application scenarios by adjusting the ratio of the two-stage degradation agent, the amount of microorganisms added, and the gradient structure ratio.

[0065] (II) Preparation method of dual-stage triggered time-controllable fully degradable materials

[0066] The preparation method provided by this invention is a specialized process adapted to the above-mentioned materials. Through multi-stage temperature control, graded feeding, stepwise addition of additives, and closed-loop post-treatment, it achieves precise control over the material's structure and function. The specific steps are as follows:

[0067] Preplasticization modification

[0068] Starch, polylactic acid, lubricant, and processing aids are added to a high-speed mixer in proportion and mixed evenly. Then, the mixture is fed into a twin-screw extruder and melt-shear plasticized within a controlled temperature range. The pre-plasticization modification of starch is completed through the coupling of heat and mechanical action, which breaks down crystallization and improves compatibility. After extrusion, the mixture is cooled and granulated to obtain pre-plasticized granules, which provide a uniform matrix raw material for subsequent copolymerization reactions.

[0069] Gradient feeding

[0070] A twin-screw extruder with a layered feeding system is used to separately feed the material into a surface layer and an inner layer. The surface layer contains fast-degrading agents, microbial synergists, and primary solvents, while the inner layer contains slow-degrading agents, inorganic reinforcing agents, and primary antioxidants. Through layered dies and gradient extrusion, a gradient structure with a continuous transition between the surface and inner layers is formed, preventing delamination and ensuring structural integrity. The surface layer accounts for 15%–25% of the total mass, and the inner layer accounts for 75%–85%, perfectly matching the gradient structure design of the material.

[0071] copolymerization

[0072] The mixture after gradient feeding is melt copolymerized at 160℃~180℃, and the copolymerization reaction time is controlled at 20h~40h. This allows the maleic anhydride grafting agent to undergo in-situ grafting and coupling reactions with polylactic acid and modified starch, forming a chemically bonded continuous copolymer phase. This improves the interfacial bonding strength and system stability, ensures grafting efficiency, and avoids excessive cross-linking.

[0073] Secondary plasticization

[0074] Plasticizers and slow-release antioxidants are added to the copolymer system, and secondary melt plasticization is carried out at 150℃~170℃ for 10h~20h. This allows the slow-release antioxidants to be uniformly dispersed in the matrix, while further reducing the melt viscosity and improving processing fluidity, providing a stable melt state for subsequent toughening and molding. The slow-release antioxidant is a microencapsulated hindered phenolic product, and the amount added is 0.2%~0.4% of the mass of the base polymer component.

[0075] Toughening modification

[0076] Toughening agents, compatibilizers, and secondary solvents are added, and the mixture is subjected to isothermal mixing and shearing at 145℃~165℃ for 10h~15h. This allows the toughening agent to be distributed in the matrix as a nano- or micron-sized dispersed phase, forming an island-structure toughening system. At the same time, the secondary solvent further promotes the uniform dispersion of each additive, eliminates local agglomeration, and improves the overall toughness of the material. The toughening agent is epoxidized soybean oil, polylactic acid elastomer, or ethylene-vinyl acetate copolymer, and the amount added is 5%~20% of the mass of the basic polymer component.

[0077] Granulation

[0078] After the toughened and modified melt is filtered through a filter screen, it is water-cooled, stretched, and pelletized to obtain fully degradable resin particles with uniform particle size and stable performance, which can be directly used in conventional plastic molding processes such as blown film, injection molding, and extrusion.

[0079] Closed-loop recycling

[0080] The solid products that are completely degraded after the materials are collected are crushed, slurryed, and sterilized before being put into an anaerobic fermentation system. Fermentation is carried out at 35℃~45℃ for 72h~96h to generate high-purity L-lactic acid with a purity of not less than 95%. After purification and refining, the fermentation products are regenerated into polylactic acid through lactide ring-opening polymerization. The regenerated polylactic acid can be directly used as the matrix raw material of the material of this invention, realizing the recycling of raw materials and forming a complete biomass closed-loop regeneration system with a raw material recycling rate of not less than 75%.

[0081] In addition, in the microbial synergistic component, the microbial agent needs to be pre-encapsulated with chitosan microspheres. The encapsulation temperature is controlled at 40℃~60℃ and the encapsulation time is 2h~4h to ensure that the encapsulation rate is not less than 85%. The particle size of the chitosan microspheres is controlled at 5~20μm to ensure that the agent can maintain its activity during the subsequent high-temperature processing and is evenly dispersed in the matrix.

[0082] The present invention will be further described in detail below with reference to several preferred embodiments and comparative examples.

[0083] Example 1: A general-purpose fully degradable material with a preset degradation cycle of 360 days

[0084] 1. Raw material ratio (parts by weight)

[0085] Basic polymer components: 42 parts tapioca starch, 58 parts L-polylactic acid, 0.5 parts stearic acid (lubricant), and 0.3 parts pentaerythritol stearate (processing aid).

[0086] Modifying additive components: 5 parts polyethylene glycol with a molecular weight of 4000, 1.8 parts maleic anhydride-grafted polylactic acid, and 2.5 parts plasticizer tributyl citrate.

[0087] Functional additive components: 10 parts of 2000 mesh heavy calcium carbonate, 0.3 parts of microencapsulated hindered phenolic antioxidant, 1.5 parts of polyaspartic acid, 12 parts of epoxidized soybean oil, 3.5 parts of primary solvent ethyl acetate, and 2.5 parts of secondary solvent acetone.

[0088] Microbial synergistic component: 0.9 parts of chitosan-encapsulated Bacillus and Pseudomonas compound bacterial agent, chitosan microspheres with a particle size of 10~15μm and an encapsulation rate of 88%.

[0089] 2. Preparation method

[0090] (1) Encapsulation of microbial agents: Chitosan is dissolved in dilute acetic acid solution, and the composite microbial agent suspension is added. The mixture is stirred and emulsified at 50°C, crosslinked and solidified for 3 hours, centrifuged, washed and dried to obtain the encapsulated composite microbial agent.

[0091] (2) Pre-plasticization modification: starch, polylactic acid, stearic acid and pentaerythritol stearate are mixed and stirred in a high-speed mixer for 10 minutes. The mixture is then transferred to a twin-screw extruder and plasticized and extruded at 155°C. The mixture is then water-cooled and granulated to obtain pre-plasticized granules.

[0092] (3) Gradient feeding: Start layered feeding. The surface layer accounts for 20% of the total mass and contains polyaspartic acid, compound bacterial agent and ethyl acetate; the inner layer accounts for 80% of the total mass and contains calcium carbonate and microencapsulated antioxidant.

[0093] (4) Copolymerization reaction: Melt copolymerization at 170℃ for 30 min to complete in-situ grafting and interfacial coupling.

[0094] (5) Secondary plasticizing: Add tributyl citrate and plasticize at 160℃ for 15 min to disperse evenly.

[0095] (6) Toughening modification: Add epoxidized soybean oil, compatibilizer and acetone, mix at 155℃ for 12 min to achieve uniform dispersion of toughening phase.

[0096] (7) Granulation and molding: melt filtration, water cooling, and pelletizing to obtain the target degradation particles.

[0097] (8) Closed-loop recycling: Collect the degradation products, anaerobic ferment at 40°C for 96 hours, purify to obtain L-lactic acid, and regenerate polylactic acid through ring-opening polymerization.

[0098] 3. Performance Test Results

[0099] Natural soil burial:

[0100] Stabilization period 0-360 days, tensile strength retention rate 86%;

[0101] The accelerated degradation period is 360-420 days, with a weight loss degradation rate of 92%.

[0102] The measured degradation cycle was 354 days, with an error of 6 days.

[0103] At a low temperature of 10℃: the degradation period is extended by 14 days, and the mechanical retention rate is 78%;

[0104] Tensile strength: 19.2 MPa; Elongation at break: 36%;

[0105] Melt flow index 2.8 g / 10 min;

[0106] L-lactic acid purity is 96%, and raw material recycling rate is 78%.

[0107] Example 2: Agricultural mulch film material with a preset degradation cycle of 240 days

[0108] 1. Raw material ratio

[0109] Differences from Example 1:

[0110] The microencapsulated hindered phenolic antioxidant contains 0.25 parts, polyaspartic acid 1.8 parts, polyethylene glycol 6 parts, compound microbial agent 1.0 part, and the surface layer accounts for 22%.

[0111] 2. Preparation method

[0112] The process parameters are the same as in Example 1, with a copolymerization temperature of 165°C and a copolymerization time of 25 min.

[0113] 3. Performance Test Results

[0114] Stability period 0–240 days, mechanical retention rate 83%;

[0115] The accelerated degradation period is 240-300 days, with a degradation rate of 91%.

[0116] The actual measurement period was 235 days, with an error of 5 days.

[0117] The cycle time was extended by 12 days under low temperature conditions, with a mechanical retention rate of 76%.

[0118] Tensile strength 17.5MPa, elongation at break 41%, suitable for blown film molding;

[0119] The recycling rate is 76%.

[0120] Example 3: Special material for long-term outdoor components with a preset degradation period of 720 days

[0121] 1. Raw material ratio

[0122] Differences from Example 1:

[0123] The microencapsulated hindered phenolic antioxidant consists of 0.4 parts, polyaspartic acid 1.0 parts, inorganic reinforcing agent of 3000 mesh talc 15 parts, toughening agent of polylactic acid elastomer 18 parts, compound bacterial agent 0.6 parts, and the surface layer accounts for 16%.

[0124] 2. Preparation method

[0125] The copolymerization temperature was 175℃, the copolymerization time was 35 min, and the secondary plasticizing temperature was 165℃.

[0126] 3. Performance Test Results

[0127] Stability period 0–720 days, mechanical retention rate 88%;

[0128] The accelerated degradation period is 720-780 days, with a degradation rate of 90%.

[0129] The actual measurement period was 713 days, with an error of 7 days.

[0130] Under low-temperature and drought conditions, the cycle was extended by 18 days, and the mechanical retention rate was 77%.

[0131] Tensile strength: 22.4 MPa; Elongation at break: 32%;

[0132] The recycling rate is 79%.

[0133] Example 4: General-purpose material toughened with ethylene-vinyl acetate copolymer

[0134] 1. Raw material ratio

[0135] Differences from Example 1:

[0136] The toughening agent was replaced with 15 parts of ethylene-vinyl acetate copolymer, the accelerated degradation agent was 1.5 parts of polyglutamic acid, and the compound microbial agent was 0.8 parts.

[0137] 2. Preparation method

[0138] Consistent with Example 1.

[0139] 3. Performance Test Results

[0140] The mechanical retention rate during the stable period was 85%, the degradation rate during the accelerated period was 93%, the degradation cycle was 358 days, and the error was 8 days.

[0141] It exhibits 79% mechanical properties in low-temperature environments, 43% elongation at break, and excellent impact resistance.

[0142] The recycling rate is 77%.

[0143] Example 5: Validation of Closed-Loop Recycling and Regeneration of Recycled Materials

[0144] The degradation products from Examples 1, 2, 3, and 4 were used to obtain regenerated polylactic acid (PLA) via fermentation polymerization, which completely replaced virgin PLA. The material was then re-prepared according to the formulation and process of Example 1, and the mixture was cycled three times consecutively. The performance was tested as follows:

[0145] First regeneration: tensile strength 18.8 MPa, degradation cycle 362 days, error 9 days;

[0146] Second regeneration: tensile strength 18.5 MPa, degradation cycle 365 days, error 10 days;

[0147] Third regeneration: tensile strength 18.2 MPa, degradation cycle 367 days, error 11 days;

[0148] The performance deviation in all three cycles was less than 5%, and the raw material recycling rate remained stable at over 75%, proving that the closed-loop process has long-term industrial stability.

[0149] Comparative Example 1: Conventional one-step blending of non-gradient, microbial-free materials

[0150] Compared with Example 1, gradient feeding was not used, no encapsulated microbial agents were added, and one-step blending granulation was used. The rest of the formulation and process were the same.

[0151] Test results:

[0152] The mechanical retention rate during the stable period was 71%, indicating significant premature degradation.

[0153] The degradation cycle fluctuates by 42 days and cannot be precisely controlled.

[0154] Under low-temperature conditions, the degradation cycle is extended by 58 days, and the degradation efficiency decreases significantly.

[0155] The tensile strength is 13.6 MPa and the elongation at break is 22%, which are significantly lower than those of the present invention.

[0156] Comparative Example 2: Materials without sustained-release antioxidants and with a single degradation aid

[0157] Compared to Example 1, the microencapsulated sustained-release antioxidant was removed, and a common organic acid was used as a single degradation aid, with no response triggering mechanism.

[0158] Test results:

[0159] The material exhibits significant mechanical degradation after 180 days, making it unable to achieve stable service for 360 days.

[0160] The degradation process is not clearly divided into stages; it is slow throughout, with a degradation rate of only 62% during the 60-day accelerated phase.

[0161] It cannot achieve timing control and does not have two-stage functionality.

[0162] This invention utilizes an integrated technical solution encompassing two-stage degradation triggering, gradient structure feeding, chitosan-encapsulated microbial synergistic catalysis, and closed-loop recycling and regeneration. The resulting fully degradable material exhibits a precisely adjustable degradation cycle within 180 to 720 days, with degradation time error controlled within ±10 days. During the preset stable period, mechanical properties are maintained at no less than 80%, and during the accelerated degradation period (60 days), the degradation rate is no less than 90%. Furthermore, it maintains excellent environmental adaptability, extending the degradation cycle by no more than 20 days and retaining mechanical properties at no less than 75% even under low-temperature (10℃) or drought conditions. The material possesses high tensile strength, excellent toughness, and good processing fluidity, making it suitable for various molding processes. The degradation products can be regenerated into polylactic acid through fermentation polymerization, achieving a raw material recycling rate of no less than 75%. Compared to conventional one-step blending, non-triggering, non-gradient structure, and non-microbial synergistic degradable materials, this invention significantly improves degradation controllability, usage stability, environmental adaptability, mechanical properties, and resource recycling rate, achieving unexpected synergistic technical effects and demonstrating outstanding substantive characteristics and significant progress.

[0163] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0164] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A two-stage triggered, time-controllable fully degradable material, characterized in that, It includes basic polymer components, modified auxiliary components, functional auxiliary components, and microbial synergistic components; The basic polymer component is a copolymer of preplasticized modified starch and polylactic acid, with lubricants and processing aids added during the preplasticization process; The modified additive components include polyethylene glycol compatibilizers, maleic anhydride grafting agents, and plasticizers; The functional additive components include an inorganic reinforcing agent, a two-stage degrading agent, a toughening agent, and a composite solvent. The two-stage degrading agent includes a stable-phase slow-release antioxidant and an accelerated-phase pH / enzyme-responsive degrading agent. The microbial synergistic component includes a chitosan-embedded Bacillus / Pseudomonas complex bacterial agent; Each component is prepared through a process of gradient feeding, preplasticization, copolymerization, stepwise addition of functional additives, and granulation.

2. The fully degradable material according to claim 1, characterized in that, In the dual-stage degradation agent, the stable-phase slow-release antioxidant is a microencapsulated hindered phenolic product, with an addition amount of 0.2%-0.4% of the mass of the basic polymer component; the accelerated-phase pH-responsive degradation agent is polyaspartic acid or polyglutamic acid, with an addition amount of 1%-2% of the mass of the basic polymer component.

3. The fully degradable material according to claim 1, characterized in that, In the microbial synergistic component, the chitosan microspheres have a particle size of 5-20 μm, the bacterial agent encapsulation rate is not less than 85%, and the addition amount is 0.5%-1.2% of the mass of the basic polymer component.

4. The fully degradable material according to claim 1, characterized in that, The gradient feeding process is adopted: the surface layer accounts for 15%-25% of the total material mass, and fast degradation aids and microbial agents are added to the surface layer; the inner layer accounts for 75%-85% of the total material mass, and slow degradation aids and inorganic reinforcing agents are added to the inner layer.

5. The fully degradable material according to claim 1, characterized in that, The material in a natural soil environment: The stabilization period is from day 0 to day T, where T is the preset degradation cycle, and the mechanical properties retention rate during this stage is not less than 80%. The accelerated degradation period is from day T to day T+60, during which the degradation rate is no less than 90%. Where T is 180 days to 720 days, and the degradation time error is no more than ±10 days.

6. The fully degradable material according to claim 1, characterized in that, The PEG-based compatibilizer has a molecular weight of 2000-6000 and is added at 3%-8% of the mass of the basic polymer component; the maleic anhydride grafting agent has a grafting rate of 0.5%-2% and is added at 1%-3% of the mass of the basic polymer component.

7. The fully degradable material according to claim 1, characterized in that, The inorganic reinforcing agent is calcium carbonate or talc powder with a particle size of 1000-3000 mesh, and the amount added is 5%-15% of the mass of the basic polymer component; the toughening agent is epoxidized soybean oil, polylactic acid elastomer or ethylene-vinyl acetate copolymer, and the amount added is 5%-20% of the mass of the basic polymer component.

8. A method for preparing a two-stage triggered, time-controllable fully degradable material, characterized in that, Includes the following steps: Pre-plasticization modification: Starch, polylactic acid, lubricant and processing aid are mixed and plasticized and granulated by twin-screw extruder at 140℃-170℃ to obtain pre-plasticized granules; Gradient feeding: A layered feeding process is adopted, with fast degradation aids, microbial agents and primary solvents added to the surface layer, and slow degradation aids, inorganic enhancers and primary antioxidants added to the inner layer; Copolymerization reaction: Copolymerize at 160℃-180℃ for 20-40 min to obtain copolymer; Secondary plasticizing: Add plasticizer and slow-release antioxidant, and plasticize at 150℃-170℃ for 10-20 minutes; Toughening modification: Add toughening agent, compatibilizer, auxiliary agent and secondary solvent, mix at 145℃-165℃ for 10-15min; Granulation: Extrusion granulation yields fully degradable resin particles; Closed-loop recycling: Degradation products are collected and polylactic acid is reprocessed through fermentation-polymerization, thus realizing raw material recycling.

9. The preparation method according to claim 8, characterized in that, The microbial agent is encapsulated with chitosan microspheres at an encapsulation temperature of 40℃-60℃ for 2-4 hours. In the closed-loop recovery step, the fermentation temperature of the degradation product is 35℃-45℃ for 72-96 hours, and the purity of the obtained L-lactic acid is not less than 95%.

10. The fully degradable material according to any one of claims 1-9, characterized in that, The material has a degradation cycle that is extended by no more than 20 days under low temperature (10℃) or dry conditions, and its mechanical properties are retained at a rate of no less than 75%. Furthermore, the degradation products can be recycled through a closed-loop fermentation-polymerization process to prepare polylactic acid, with a raw material recycling rate of no less than 75%.